Having a trip abroad is certainly good for the old couple, but it remains whether they will enjoy it.
A. to see
B. to be seen
C. seeing
D. seen
网友回答
A. to see
(答案→)B. to be seen
C. seeing
D. seen
解析：remain 作“尚需”解，要接不定式作表语，see 与 it(形式主语，指whether they will enjoy it)是动宾关系，因此用不定式的被动式。